1. Field of the Invention
The present invention relates to a flexible printed circuit board, and, more particularly, to a flexible printed circuit board connected to a printer head, which provides improvement in printing speed through impedance reduction.
2. Description of the Related Art
In general, printing machines, such as an inkjet printer or a duplicating machine, form an image using an ink cartridge. The ink cartridge emits, to a printing paper, a monochromatic or color ink stored in the ink cartridge through a printer head according to a printing command signal, i.e., according to a heater selection signal provided from the printing machine. The printer head is a substrate for firing ink, and is formed on a part of the ink cartridge.
Meanwhile, there is a need for a device that transfers a heater selection signal provided from the printing machine to the printer head, and a flexible printed circuit (FPC) board is generally used to transfer this heater selection signal. An FPC board is a printed circuit board that electrically connects the printing machine and the printer head.
The following description will be made using an inkjet printer as an example for the printing machine.
FIG. 1 is a plan view schematically showing a part of an FPC board connected with the printer head as in the related art.
Referring to FIG. 1, a conventional FPC board 100 includes a plurality of voltage supplying terminals 110, a plurality of grounded terminals 120, a plurality of signaling terminals 130, a plurality of first cables 115, and a plurality of second cables 125. Here, the voltage supplying terminals 110, the grounded terminals 120, and the signaling terminals 130 are represented by the reference numerals P, G, and S, respectively.
The voltage supplying terminals 110 are operated for each color, and supply a voltage according to a printing command signal received from the inkjet printer. The grounded terminals 120 are used for grounding the FPC board 100, and one voltage supplying terminal 110 has at least two grounded terminals 120. The signaling terminals 130 are used for performing relevant functions according to a controlling signal received from the inkjet printer.
The first cable 115 is a wiring for electrically connecting the voltage supplying terminal 110 to the first bonding pad 152 on the printer head 150, which will be described in the following. The second cable 125 is a wiring for electrically connecting the grounded terminal 120 to the second bonding pad 154 on the printer head 150. A wiring (not shown) for connecting the signaling terminal 130 to the printer head 150 will be omitted.
Also, the printer head 150, having a plurality of heaters (not shown) to discharge ink, is provided on one side of the ink cartridge, and has a plurality of the first bonding pads 152 and the second bonding pads 154. A description and drawing of other elements provided to the printer head 150, such as an FET (Field Effect Transistor) element, will be omitted.
A plurality of the first and second bonding pads 152, 154 are distributed and provided at both sides of the printer head 150, i.e., to the first side edge and the second side edge. The first and the second bonding pads 152, 154, made of aluminum, are terminals which are bonded to the leads, respectively, of the first and the second cables 115, 125 by ultrasonic fusing.
The printer head 150, provided at one side of the ink cartridge, fires ink according to a printing command signal received from the inkjet printer through the FPC board 100.
If a printing command signal is received, an impedance formed at the heater (not shown) connected with the voltage supplying terminal 110 (e.g. Y1-P), and at least two grounded terminals 120 (e.g. Y1-G), is influenced by a resistance, a capacitance, and an inductance, but is mostly greatly influenced by the inductance. Namely, impedance increases as inductance value increases.
Table 1 shows inductance values measured at the FPC board 100 connected with the printer head of FIG. 1.
TABLE 1ColorInductance (unit: nH)Y136.8Y221.0M138.1M222.9C135.0C221.3
Referring to Table 1 and FIG. 1, Y is a group for realizing yellow, M for magenta, C for cyan, and 1, 2 in the ‘color’ block of the Table 1 indicates that color groups Y, M, C are connected to the first side and the second side of the printer head 150, respectively. Also, Y1 consists of one voltage supplying terminal Y1-P and two grounded terminals Y1-G, for realizing yellow color. As the construction of Y2, M1, M2, C1, C2 is similar to that of Y1, a detailed description thereof will be omitted.
As in FIG. 1, in the case that the first cable 115 and the second cable 125 at a predetermined group Y1 are separated from each other by more than a predetermined distance and provided to the FPC board 100, or in the case that the first and the second cables 115, 125 are nearly the same in their diameter, the conventional FPC board 100 has high inductance values as shown in Table 1.
Also, the conventional inkjet printer requires maximum data transmission frequency of 10 MHz–100 MHz for high speed printing. Namely, if printing is performed with the use of a high frequency wave at the status of high inductance of the FPC board 100 as shown in Table 1, the impedance increases and a current supply loss subsequently occurs. Accordingly, the FET element (not shown) for operating the printer head 150 cannot receive the necessary current amount, so that the heater (not shown) is not properly heated and printing speed may not be increased, or may be delayed.